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gojwtrsajwt-go

Problem with generating jwt token RS256 with dgrijalva/jwt-go package


Why I allways get the "key is invalid" error in the simple code bellow. I already tried to use different private keys with the same result. Please help me cause I have no more ideas what i am doing wrong.

package main

import (
    "fmt"
    "log"

    "github.com/dgrijalva/jwt-go"
)

var key = `-----BEGIN RSA PRIVATE KEY-----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-----END RSA PRIVATE KEY-----`

func main() {
    token := jwt.New(jwt.SigningMethodRS256)
    jwt, err := token.SignedString(key)
    if err != nil {
        log.Println(err)
    }
    fmt.Println("jwt=", jwt)
}

the output:

2021/04/06 16:48:52 key is invalid

jwt= what is wrong with my key?

I`ve generated it with:

ssh-keygen -t rsa -P "" -b 2048 -m PEM -f jwtRS256.key
ssh-keygen -e -m PEM -f jwtRS256.key > jwtRS256.key.pub

Thank you


Solution

  • The RSA family algorithms expect a key of type *rsa.PrivateKey. The library dgrijalva/jwt-go has a helper function jwt.ParseRSAPrivateKeyFromPEM(keyData) where keyData is a []byte slice.

    The repo has some handy examples in rsa_test.go file.

    Also the examples are outdated because as of Go 1.16 the ioutil package is deprecated...


    Warning!

    Please be aware that github.com/dgrijalva/jwt-go has been unmaintained for a long time and has critical unfixed bugs. And doesn't support Go modules, before the version 4 (which is just a preview anyway). I strongly recommend to choose an different library for dealing with JWT.

    Update June 2021

    There is now an official community fork of the library: golang-jwt/jwt blessed by the owner of the original project.